Centrifugal cleaners have been employed for many years in the paper industry for removing small particles of higher specific gravity than paper fibers from slurries of paper making fiber, especially waste paper stocks.
In centrifugal cleaners used for that purpose, in what is hereinafter referred to as "conventional centrifugal cleaning technique," the discharge outlet at the apex (tip) of the cylindrical-conical vessel is relatively small in comparison with the inlet and accepts outlets, e.g. 1/8 inch in diameter as compared with 5/8 inch diameters for the other two ports in a conventional cleaner 3 inches in diameter. In such conventional cleaning operations, therefore, the reject discharge through the apex outlet is correspondingly small in comparison with the accepts flow, e.g. 3% and 97% by volume respectively.
In comparatively recent years, there has been an increasing use of centrifugal cleaners to separate good paper fibers from contaminants of closely similar or lower specific gravity such that they cannot be readily separated by conventional centrifugal cleaning technique.
In general, cleaners for such "reverse" centrifugal cleaning have been made by modifying the construction and/or operation of a conventional cleaner to provide operating conditions which cause the good fiber to be discharged through the apex outlet as the accepts flow while the lights are discharged as reject through the base (top) outlet which is the accepts outlet in conventional centrifugal cleaning. For an extended discussion of prior and up dated reverse centrifugal cleaning developments, reference is made to Seifert et al. U.S. Pat. No. 4,155,839 wherein the present inventor was a joint patentee.